Page 218 - Root Cause Failure Analysis
P. 218
206 Root Cause Failure Analysis
Straight - flow Angle - flow
Cross - flow
Figure 17-5 Three globe valve configurations: straightjlow, angle flow, and cross &w.
on the disk to cause uneven wear. The rate at which fluid flows through the valve is reg-
ulated by the position of the disk in relation to the valve seat.
The globe valve should never be jammed in the open position. After a valve is fully
opened, the handwheel or actuating handle should be closed approximately one-half
turn. If this is not done, the valve may seize in the open position making it difficult, if
not impossible, to close the valve. Many valves are damaged in the manner. Another
reason to partially close a globe valve is because it can be difficult to tell if the valve is
open or closed. If jammed in the open position, the stem can be damaged or broken by
someone who thinks the valve is closed.
Performance
Process-control valves have few measurable criteria that can be used to determine
their performance. Obviously, the valve must provide a positive seal when closed.
View A View B
Figure 17-6 Globe valve.
